Orthogonal frequency division multiplexing (OFDM) is a form of multiplexing that distributes data over a number of carriers that have a very precise spacing in the frequency domain. The precise spacing of the carriers provides several benefits such as high spectral efficiency, resiliency to radio frequency interference and lower multi-path distortion. Due to its beneficial properties and superior performance in multi-path fading wireless channels, OFDM has been identified as a useful technique in the area of high data-rate wireless communication, for example wireless metropolitan area networks (MAN). Wireless MAN are networks to be implemented over an air interface for fixed, portable, and mobile broadband access systems.
In some wireless networks, a mobile station (MS) in a given cell is only served by its serving base station (BS).
One drawback of such wireless networks is that MSs near an edge of the given cell suffer performance loss due to interference from other cells in cellular networks and propagation loss in non-cellular networks which results in limited data rates and gaps in coverage of the given cell.
While soft hand off can be used in cellular networks to improve performance to some extent for MSs at the cell edge, the improved performance comes at the cost of additional system complexity and a spectrum efficiency penalty.
One way to improve the performance is to introduce a fixed or mobile relay station (RS) into wireless networks. The use of an RS may provide a) enhanced system capacity, b) enhanced data rate and cell coverage, c) reduced MS transmit power requirements and d) allow less expensive power amplification.